Magnetic therapy is not new. For hundreds of years, magnets have been used to treat a wide variety of medical conditions. Today, electromagnetic (i.e., devices that use an electric current to produce a magnetic field) therapy is garnering increasing public awareness as a natural or complementary alternative for the treatment of illness and chronic pain. In recent years, the impact of treatment with electromagnetic fields on physical ailments has been presented in peer-reviewed scientific studies. More studies are underway as the interest in electromagnetic therapies escalates. As a result, the electromagnetic products industry is growing rapidly.
Electromagnetic therapy systems may be used to treat a variety of conditions and ailments through the application of a magnetic field to a human or other subject. The impressed magnetic field may range widely depending on the therapeutic method and the condition being treated. For example, a magnetic flux density of 2 Teslas may be used in transcranial magnetic stimulation therapy (TMS), while fields as low as the pico-Tesla range may be applied for conditions such as Parkinson's disease and epilepsy according to the Jacobson magnetic therapy protocol, as described in U.S. Pat. Nos. 5,269,746 and 5,366,435.
Many electromagnetic therapy systems produce low-level magnetic fields in the micro-Tesla range and below, over frequencies of a few hundred Hertz, down to DC. These magnetic fields are typically generated using magnetic coils that are driven by low-current levels (e.g., micro-amperes and lower) created by drivers which include an off-the-shelf signal generator in series with a manual attenuator, (e.g., a manual switch-box containing discrete resistors). The magnetic coil used may be a Helmholtz coil, which produces an especially uniform field, although many other coil configurations are possible (e.g., a solenoid, a poloidal coil, a toroid etc.).
A limitation present in known systems is a lack of precision and accuracy due to electronic errors resulting from non-linearity and stray AC and DC offsets. Non-linearity and stray AC and DC offsets can be caused by using commercial-grade and consumer-grade components. A known way to limit non-linearity and stray AC and DC offsets may be to use laboratory-grade components. However, laboratory-grade components are much more expensive than commercial or consumer-grade components.